Smart cards (also referred to as integrated circuit (IC) cards), are well known mobile data processing devices with a built-in central processing unit (CPU). An IC card generally includes an IC card substrate in which IC card devices are integrated. An IC card also may include an abnormal condition detection circuit that detects an abnormal condition in the smart card, and a reset signal generator that generates a reset signal for resetting the overall operation of the smart card in response to a signal output from the abnormal condition detection circuit, so as to reduce or prevent damage to the smart card due to a change in an external environment and/or prevent security breaches.
FIG. 1 is a block diagram of a conventional smart card 10. Referring to FIG. 1, the smart card 10, which is an IC card or a chip, includes an IC card substrate 28 which may be fabricated of paper and/or plastic. Included in the substrate 28 are a CPU 12, a random access memory (RAM) 14, a read-only memory (ROM) 16, a non-volatile memory 18, a peripheral circuit 20, and a security circuit 22. The non-volatile memory 18 may be embodied as EEPROM (electrically erasable and programmable ROM).
The CPU 12 executes an operating system (OS) program. The RAM 14 stores data generated when the CPU 12 executes the OS program. The ROM 16 stores the OS program and other programs. The non-volatile memory 18 stores various application programs and predetermined data controlled by the CPU 12.
The security circuit 22 includes an abnormal condition detector 24 and a reset signal generator 26. When at least one of ambient conditions (voltage, frequency, temperature, light, and so on) of the CPU 12 or the smart card 10 in which the CPU 12 is implemented, does not fall within a predetermined range, e.g., specifications, the abnormal condition detector 24 detects the at least one ambient condition, generates a detection signal DET as the detecting result, and outputs the detection signal DET to the CPU 12 and the reset signal generator 26. Then, the CPU 12 recognizes that the at least one abnormal condition occurs in the smart card 10, in response to the detection signal DET.
The reset signal generator 26 generates a reset signal RST for resetting the CPU 12, the non-volatile memory 18, and the peripheral circuit 20, in response to the detection signal DET.
A smart card, such as that illustrated in FIG. 1, is directly reset when an abnormal condition due to a change in an internal and/or external environment is detected therein. Since the smart card is reset, a user generally can neither learn about the abnormal condition that causes the smart card 10 to be reset, nor recover the data stored in the RAM 14, which is a volatile memory, since the data is initialized upon reset.
Korean Published Patent Applications 10-0471147 and 10-2004-0106075, Japanese Patent Application 2003-021797, and U.S. Pat. No. 5,465,349 describe circuits for IC cards that allow detection information and/or other information to be stored prior to a reset.